Javascript regex for matching twitter-like hashtags

I'd like some help on figuring out the JS regex to use to identify "hashtags", where they should match all of the following:

1. The usual twitter style hashtags: #foobar
2. Hashtags with text preceding: abc123#xyz456
3. Hashtags with space in them, which are denoted as: #[foo bar] (that is, the [] serves as delimiter for the hashtag)

For 1 and 2, I was using something of the following form:

var all_re =/\S*#\S+/gi;

I can't seem to figure out how to extend it to 3. I'm not good at regexps, some help please?

Thanks!